 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.osgi.framework.internal.core;

 import java.io.IOException ;
 import java.net.URL ;
 import java.util.*;
 import org.eclipse.osgi.service.resolver.BundleDescription;

 /**
  * DependentPolicy is an implementation of a buddy policy.
  * It is responsible for looking up a class in the dependents of the bundle
  * to which this policy is attached to.
  */
 public class DependentPolicy implements IBuddyPolicy {
     BundleLoader buddyRequester;
     int lastDependentOfAdded = -1; //remember the index of the bundle for which we last added the dependent
 List allDependents = null; //the list of all dependents known so far

     public DependentPolicy(BundleLoader requester) {
         buddyRequester = requester;

         //Initialize with the first level of dependent the list
 allDependents = new ArrayList();
         basicAddImmediateDependents(buddyRequester.getBundle().getBundleDescription());
         //If there is no dependent, reset to null
 if (allDependents.size() == 0)
             allDependents = null;
     }

     public Class loadClass(String name) {
         if (allDependents == null)
             return null;

         Class result = null;
         //size may change, so we must check it every time
 for (int i = 0; i < allDependents.size() && result == null; i++) {
             BundleDescription searchedBundle = (BundleDescription) allDependents.get(i);
             try {
                 BundleLoaderProxy proxy = buddyRequester.getLoaderProxy(searchedBundle);
                 if (proxy == null)
                     continue;
                 result = proxy.getBundleLoader().findClass(name, true);
             } catch (ClassNotFoundException e) {
                 if (result == null)
                     addDependent(i, searchedBundle);
             }
         }
         return result;
     }

     private synchronized void addDependent(int i, BundleDescription searchedBundle) {
         if (i > lastDependentOfAdded) {
             lastDependentOfAdded = i;
             basicAddImmediateDependents(searchedBundle);
         }
     }

     public URL loadResource(String name) {
         if (allDependents == null)
             return null;

         URL result = null;
         //size may change, so we must check it every time
 for (int i = 0; i < allDependents.size() && result == null; i++) {
             BundleDescription searchedBundle = (BundleDescription) allDependents.get(i);
             BundleLoaderProxy proxy = buddyRequester.getLoaderProxy(searchedBundle);
             if (proxy == null)
                 continue;
             result = proxy.getBundleLoader().findResource(name, true);
             if (result == null) {
                 addDependent(i, searchedBundle);
             }
         }
         return result;
     }

     public Enumeration loadResources(String name) {
         if (allDependents == null)
             return null;

         Enumeration results = null;
         //size may change, so we must check it every time
 for (int i = 0; i < allDependents.size(); i++) {
             BundleDescription searchedBundle = (BundleDescription) allDependents.get(i);
             try {
                 BundleLoaderProxy proxy = buddyRequester.getLoaderProxy(searchedBundle);
                 if (proxy == null)
                     continue;
                 results = BundleLoader.compoundEnumerations(results, proxy.getBundleLoader().findResources(name));
                 addDependent(i, searchedBundle);
             } catch (IOException e) {
                 //Ignore and keep looking
 }
         }
         return results;
     }

     private void basicAddImmediateDependents(BundleDescription root) {
         BundleDescription[] dependents = root.getDependents();
         for (int i = 0; i < dependents.length; i++) {
             BundleDescription toAdd = dependents[i];
             if (toAdd.getHost() == null && !allDependents.contains(toAdd)) {
                 allDependents.add(toAdd);
             }
         }
     }
 }

